1. Field of the Invention
The present invention generally relates to semiconductor devices, and more specifically, to a semiconductor device having a heat spreader configured to radiate heat from a semiconductor element.
2. Description of the Related Art
In a semiconductor device installed in an electronic machine, heat generated at the semiconductor device by operation of a semiconductor element is transferred from a rear surface of the semiconductor element via a heat conductive layer such as heat conductive resin, or silver paste to a heat spreader so as to be radiated.
However, as today's electronic machines have high function or high operability, it is required that the semiconductor devices applied to the electronic machines also have high functionality or high operability. Electric power consumed by the semiconductor element at the semiconductor device is also increasing and therefore the amount of heat generated by the semiconductor element is increasing.
Because of this, it is difficult to sufficiently transfer the heat generated by the semiconductor element to the heat spreader by the above-mentioned heat conductive resin, silver paste, or the like.
Because of this, it has been suggested that a soldering alloy having heat conductivity higher than the heat conductive resin, the silver paste, or the like be used so that the heat generated by the semiconductor element is transferred to the heat spreader so as to be efficiently radiated.
For example, a semiconductor device having an insulation substrate, a heat sink fixed on the insulation substrate, and a semiconductor element fixed by a soldering material on the heat sink, is disclosed in Japanese Laid-Open Patent Application Publication No. 2003-124438. A semiconductor element placement surface having a substantially same configuration as that of a rear surface of the semiconductor element, the semiconductor element placement surface being where the semiconductor element is placed, and a groove surrounding the periphery of the semiconductor element placement surface are provided on an upper surface of this heat sink. The semiconductor element is fixed by the soldering material provided on the semiconductor element placement surface so as to fill the groove. A re-molten soldering material is held on the placement surface and in the groove.
On the other hand, low voltage operation of the semiconductor devices is progressing. Hence, a signal handled by the semiconductor device may be interfered with by electric power noise or cross talk noise.
Because of this, in the electronic machine, a bypass condenser is provided between an electric power source of the semiconductor device and ground so that the entry of external noise causing an error in operation of the semiconductor device is reduced. Normally, such a bypass condenser is provided on a printed circuit board which is a support board where the semiconductor element is mounted.
The support board may be called an interposer.
On the other hand, a thermistor may be provided on the printed circuit board so that the amount of heat generated by the semiconductor element is monitored.
However, in the semiconductor device having a passive element such as the thermistor or a capacitive element such as the condenser, if the soldering alloy is used as a heat combining body between the semiconductor element and the heat spreader so that the heat generated by the semiconductor element is transferred to the heat spreader, when heat is applied in a mounting process of the semiconductor device to the support board, melting of the soldering alloy may be generated.
Because of this, the molten soldering alloy is caused to flow on the surface of the heat spreader so as to flow in the vicinity of the passive element such as the condenser or the thermistor and come in contact with an electrode of the passive element. As a result of this, a short between the electric power source of the semiconductor device and ground may be caused.
In the example discussed in Japanese Laid-Open Patent Application Publication No. 2003-124438, if the metal plating is applied in the groove, the solder may flow from the groove to the outside due to bad wetting.